Electrohydraulic control arrangement

ABSTRACT

An electrohydraulic control valve has a slider spool valve body to connect, or disconnect a double-acting hydraulic power device from a source, or a drain, respectively; a spring maintains the spool valve in centered position. The spool valve is further provided with a double-acting control piston having faces of unequal size, slidable in a chamber, and electromagnetic on-off valves interconnect the piston chambers formed by the two sides of the double faced piston, with the and drain of the hydraulic pressure fluid respectively, to shift the position of the control piston and hence of slider.

Unit-ed States Patent 7 ,lnventor Manfred Kramer Fellbach-Lindle. Germany Appl. No. 795,273 Filed Jan. 30, 1969 Patented A Jan. 19, 1971 Assignee Robert Bosch GmbH Stuttgart, Germany a limited liability company of Germany Priority Apr. 24, 1968 Germany ELECTROHYDRAULIC CONTROL ARRANGEMENT 4 Claims, 6 Drawing Figs.

11.8. CI 137/625.64 Int. Cl Fl6k 11/07 Field ofSearch 137/6256,

[56] References Cited UNITED STATES PATENTS 2,898,936 8/1959 Collins l37/625.63 2,916,051 12/1959 Taylor l37/625.64 2,993,510 7/1961 Collins 137/625.64 3,129,645 4/1964 Olmstead l37/625.64X 3,434,390 3/1969 Weiss l37/625.64X

Primary Examiner-Henry T. Klinksiek AttorneyFlynn & F rishauf ABSTRACT: An electrohydraulic control valve has a slider spool valve body to connect, or disconnect a double-acting hydraulic power device from a source, or a drain, respectively; a spring maintains the spool valve in centered position. The spool valve is further provided with a double-acting control piston having faces of unequal size, slidable in a chamber, and electromagnetic on-off valves interconnect the piston chambers formed by the two sides of the double faced piston, with the and drain of the hydraulic pressure fluid, respectively, to shift the position of the control piston and hence of the slider.

' of a power device.

ing piston. When the spool slider is in a centered, neutral position, the power device is separated from the source of pressure fluid. Shifting the spool slider laterallyconnects the power device with a source of hydraulic pressure fluid,,or a drain, respectively. The position of the spool-typeslider itself is controlled by hydraulic pressure fluid which is admitted to opposite sides of a double-acting piston by opening or closing of electromagnetic valves.

It has been previously proposed to control spool-type slider by means of a multiposition valve (see, for example, German Pat. No. l,l88,398 for example byafour-way three-position valve. The spool slider is hollow and is'provided with a drive piston which is constantly subjected to pressure fluid. An auxiliary slider, electromagnetically operated and located within the spool slider controls drainage from one, or the other side .of the drive piston. Such an arrangement requires a doubleacting magnetic drive which is fairly complicated and expensive, particularly since the magnetic drive must have a displacement both in amount and direction which corresponds to the displacement of the spool slider. Additionally, manufacture of hollow sliders is relatively expensive.

An electrohydraulic control arrangement capable of controlling both the direction as well as the speed of displacement of a power device has been disclosed in US. Pat. No. 3,l29,645. The slider of a four-way valve, capable of assuming intermediate positions between a centered position and a pair of terminal positions is controlled by a pair of electromagnetically operated pilot valves. Each pilot valve controls five ducts and can assume two positions. This arrangement requires constrictions, check valves as well as a specific arrangement of both pilot valves with respect to each other, so that control of both direction and speed of a power devicecan be obtained only at relatively high expense. It is an object of the present invention to provide a simple electrohydraulic control arrangement capable of remotely controlling the direction and speed S UBJECT MATTER OF THE PRESENT INVENTION Briefly, the control slider is provided with a differential piston having a larger anda smaller acting surface, on opposite sides. The piston is slidable in a chamber, which is subdivided into two parts by the piston. The smaller chamber is connected to a pressure source and further over an on-off electromagnetically operated valve with the chamber associated with the larger surface of the piston. A second on-off electromagnetically operated valve connects the chamber to the return, or drain line of the hydraulic fluid. A simple structure results and control can readily be obtained without complication. Two similar electromagnetically operated on-off valves are all that is necessary and the ducting is likewise simple. Control arrangements made in accordance with the present invention thus can readily be used on movable parts.

The control arrangement can readily be made fail-safe with respect to electric power supply, andto accommodate various design requirements. The arrangement canbe designed so that the spool slider will assume its neutral position upon interruption of electrical current, thus blocking the utilization device hydraulically; alternatively, the control slider can be held by the electromagnetic valves in its previous commanded position, thus maintaining the speed of 'theutilization device at a constant level. 1

The invention will n w be described by way of example with reference to the accompanying drawing, wherein:

FIGJ is a cross-sectional view through a hydraulic control arrangement, partly schematicall indicating a first position of the pilot valve;

FIG. 2 illustrates, schematically, a second position of the pilot valves, moving the spool slider in one direction;

FIG. 3 is a third position of the pilot valves, hydraulically blocking the spool slider; and

FIG. 4 is a fourth position of the pilot valves, moving the spool slider in the opposite direction.

The electrohydraulic control arrangement comprises a housing 10 having a pressure duct 11 to be connected to a line 13 coming from a pump 12; housing 10 is further formed with a drain or return duct '14, as well as with two ducts 15, 16 connected to a utilization device 17, such as a double-acting piston 17.

The housing 10 is formed with a bore 18, in which a spool slider 19 can slide back and forth. Bore 18 is formed with seven enlargements, forming chambers 21, 22, 23, 24, 25, 26 and 27; the central chamber 24 is connected with the inlet pressure duct 11. Chamber 23 and 25, on both sides of inlet chamber 24, connect with ducts 15 and 16 leading to the utilization device 17; the outermost chambers 22 and 26 connect with the returnline I4 and serve as drainage chambers.

Control slider 19 is subdivided by a pair of circular grooves 28,29 into three sections 31, 32, 33. When the spool slider 19 is in its neutral position, as indicated in FIG. 1, the chambers 22, 23, 24, 25, and 26 are separated from each other. A double-acting centering'device 34, well known in the art, is inserted in one terminal chamber 21, maintaining the spool slider 19 in centered position. The other end of slider 19 extends into a chamber 27, and is provided with a differential piston 36, Differential piston 36 subdivides chamber 27 into a space 37, at the side of differential piston 38 which is the smaller face, and into a chamber 39 at the side of the larger face 41 of the differential piston. The free volume of chamber 37 will be less than the free volume of chamber 39.

Chamber 37 is connected by means of a duct 42, having a constriction in the form of a choke 43 therein with the inlet pressure line 11. Chamber 39 is connected over a duct 44, in which an electromagnetically controlled valve 45 is inserted, with the return or drain line 14. A cross connecting duct 46, in which an electromagnetic valve 47, similar to valve 45 is inserted, interconnects the two chambers 37 and 39.

Each one of the electromagnetically controlled valves 45,

47 are of the type that is open when not energized. Springs 48, 49 respectively, permit adjustment of the operation of the valves. When the magnet is energized, the valve closes. Valves 45, 47 can be energized independently by respectively associated switches 50, 51, v a

Operation:

As illustrated in FIG. 1, the electromagnetically operated valves 45,47 are not energized so that the valves are maintained open by their springs. The spool slider 19 is thus maintained in a centered position only by the centering device 34, independent of any hydraulic pressure, and thereby seals the chambers 23, 25 connected to the utilization device from the inlet as well as the drainage ducts l1, 14, by sealing against chamber 24 and return line chambers 22, 26.

Energization of electromagnetically controlled valve 45,

and the established fluid flows is illustrated in FIG. 2. Interconnection of chamber 39 with the drainage line 14 over duct 44 is interrupted; pressure fluid will thus pass from supply 11 over constriction 43 into chambers 37' and 39, on both sides of the differential piston 36. Due to the unequal volume of the chambers, and the unequal size of the faces of the piston, the piston 36 and thus the spool slider 19 will move towards the left (with respectto FIG. 1) counter the spring pressure of the centeringdevice 34. Portions 31 and 32 of thespool slider then connect the central inlet chamber 24 with the utilization chamber 25, and further interconnect the return from the utilization device 17 to chamber 23 and then to return chamber 22. Fluid under pressure can thus reach the utilization device, and fluid can be drained from the utilization device, and piston 17 will move towards the left (FIG. 1) with increasing acceleration. If piston 17' has reached a desired speed which is to be maintained, valve 47 is additionally ener gized and the fluid path will be as seen in FIG. 3. Chamber 39 is then isolated by both valves 45 and 47, blocking further movement of spool slider 19, and maintaining the existing position thereof, so that the piston 17' of the utilization device will move towards the left with"'uniform speed.

lf it is desired to retain the piston of the utilization device in its instantaneous position, both valves 45 and 47 are deenergized so that they will open. They will thus again assume the position illustrated in FIG. 1, the centering device 34 will quickly center the spool slider 19 in its central, neutral position, and hydraulically blocking piston 17' in its position.

If it is desired to move the utilization piston 17' towards the right, valve 47 is operated and the fluid path will be as illustrated in FIG. 4. Fluid under pressure will flow from pressure line 11 only into chamber 37. Accelerating movement of piston 17 can be changed to movement at uniform speed as above described.

The hydraulic control arrangement according to the present invention thus enables remote control of an utilization piston at uniform speed, at accelerating speed, or at decelerating speed, as well as maintaining the piston in any particular desired position.

Fine control arrangements, well known in the art, may additionally be used.

Ordinary commercially available on-off valves, having positively seating movable valve bodies, seating against conical valve seats are suitable for the valves 45, 47. They are simple and provide better sealing with respect to slider-type valves or gate valves. Instead of constriction 43, a fluid flow limiting valve can also be used.

The present invention has been described in connection with a double-acting utilization device. The control arrangement of the present invention can also be used with single-acting utilization element. The control arrangement as illustrated blocks if the electrical current should be interrupted, so that a fail-safe arrangement is provided. If desired, the electrically operated valves can be of the type which is normally closed and opens only when energized so that, upon failure of electrical power, the fluid flow arrangement will be as illustrated in H0. 3.

I claim:

1. Electrohydraulic control valve for a hydraulic power device (17, 17' said valve having:

a valve housing formed with a slider bore (18) and a control piston chamber (37, 39); 2. a spool slider l9) slidable in said bore;

supply duct means interconnecting said bore with a pressure line (11, l3)andareturnline (14); 7 operating duct means (15,' 16) for interconnecting said slider bore with said power device, said spool valve interrupting communication between sa id'supply ductmcans and said operating duct means when said spool valve is in centered position; and l I means controlling the position of said spool slider 19) comprising: i centering mearis (34) to center said spool slider and maintain said slider centered in said bore;

a differential control piston (36) having a larger (41) and a smaller (38) acting surface connected to said spool slider, said piston being slidable in said control piston chamber (37, 39) and subdividing said chamber into a first, smaller chamber (37) and a second, larger chamber (39);

a first electromagnetically operated valve means (4 7)and a connecting duct (46) interconnecting and controlling flow between said first and said second chamber;

a first duct (42) directly connecting said first smaller chamber (37) andsaid pressure line; and

a second valve means(45) and a second duct (44) connected to and controlling flow from said secondlarger chamber (39) to the return line whereby, when both electromagnetic valve means (45, 47) are closed, the second, larger chamber is isolated from the supply line (11) by the closed first valve means (47) and from the return line (14) by the closed second valve means (45) and the differential control piston (36) will remain in the position commanded by said hydraulic fluid admitted to the respective chambers before closing of both said valve means. 2. Valve according to claim 1 wherein said centering means (34) and said differential piston are connected to said spool slider (19) at opposite ends thereof.

3. Valve according to claim 1 wherein said electromagnetic valves are normally open and close when electrically enerized.

g 4. Valve according to claim 1, including a constriction (43) in the first duct (42) connecting said smaller chamber (37) to said pressure line (11), 

1. Electrohydraulic control valve for a hydraulic power device (17, 17''), said valve having: a valve housing (10) formed with a slider bore (18) and a control pisTon chamber (37, 39); a spool slider (19) slidable in said bore; supply duct means interconnecting said bore with a pressure line (11, 13) and a return line (14); operating duct means (15, 16) for interconnecting said slider bore with said power device, said spool valve interrupting communication between said supply duct means and said operating duct means when said spool valve is in centered position; and means controlling the position of said spool slider (19) comprising: centering means (34) to center said spool slider and maintain said slider centered in said bore; a differential control piston (36) having a larger (41) and a smaller (38) acting surface connected to said spool slider, said piston being slidable in said control piston chamber (37, 39) and subdividing said chamber into a first, smaller chamber (37) and a second, larger chamber (39); a first electromagnetically operated valve means (47) and a connecting duct (46) interconnecting and controlling flow between said first and said second chamber; a first duct (42) directly connecting said first smaller chamber (37) and said pressure line; and a second valve means (45) and a second duct (44) connected to and controlling flow from said second larger chamber (39) to the return line, whereby, when both electromagnetic valve means (45, 47) are closed, the second, larger chamber is isolated from the supply line (11) by the closed first valve means (47) and from the return line (14) by the closed second valve means (45) and the differential control piston (36) will remain in the position commanded by said hydraulic fluid admitted to the respective chambers before closing of both said valve means.
 2. Valve according to claim 1 wherein said centering means (34) and said differential piston are connected to said spool slider (19) at opposite ends thereof.
 3. Valve according to claim 1 wherein said electromagnetic valves are normally open and close when electrically energized.
 4. Valve according to claim 1, including a constriction (43) in the first duct (42) connecting said smaller chamber (37) to said pressure line (11). 